1. Field of the Invention
The present invention relates to a semiconductor pressure sensor, and more particularly, to a mounting structure thereof.
2. Background Art
A semiconductor pressure sensor has been proposed in which a thin film section called a diaphragm section is formed on a silicon substrate by a micro-machining technique using the properties of silicon as an elastic body, and pressure changes are converted into electric signals. In particular, a piezoresistance-type semiconductor pressure sensor which detects distortion of a diaphragm section as a resistance value change in diffusion resistance using the piezoresistance effect of silicon has been widely used for applications which particularly use a corrosive gas, a conductive liquid or the like as a pressure detection target fluid, using the chemical stability of silicon. An example of such a semiconductor pressure sensor in the related art is illustrated in FIG. 17 (for example, JP-A-09-250964). This semiconductor pressure sensor uses a sensor chip 101 which is obtained by processing a semiconductor substrate and forming a thin film diaphragm section 101a and a piezoresistor 111, which detects distortion of the diaphragm section 101a due to pressure and is fixed to a glass base 102. Here, an opening section of a main body 112 which is formed in an approximately box shape, and has the sensor chip 101 mounted therein, is closed by a stainless steel diaphragm 113. Further, a silicon oil 114 is sealed inside the main body 112. Further, terminals 116 are sealed to the main body 112 through a hermetic seal 115. Further, the terminals 116 are connected with the piezoresistor 111 of the sensor chip 101 through bonding wires 117. That is, a pressure detection target fluid P is in contact with the outer side of the stainless steel diaphragm 113, and pressure which the stainless steel diaphragm 113 receives from the pressure detection target fluid is transmitted to the diaphragm section 101a of the sensor chip 101 through the silicon oil 114 inside the main body 112, thereby making it possible to detect the pressure of the pressure detection target fluid.
However, in this configuration, since the silicon oil 114 which is a pressure guiding medium is sealed inside the main body 112 and the stainless steel diaphragm 113 is used to transmit the pressure to the silicon oil 114, the structure becomes complicated and the cost becomes high. Further, the size becomes large, thereby making it difficult to realize a small-sized sensor. Further, the detection accuracy of the sensor chip 101 deteriorates due to the influence of the reactive force of the stainless steel diaphragm 113.
Thus, as shown in FIGS. 18A to 18C, a pressure sensor has been proposed which has a mounting structure in which an atmosphere inlet port 212 and a pressure inlet port 211 are disposed to oppose each other with reference to a sensor chip 220 which employs a thin film diaphragm section (JP-A-2009-52988). A reference numeral 210 represents a main body, and a reference numeral 231 represents lead frames. FIG. 18A is a top view illustrating the pressure sensor, FIGS. 18B and 18C are a side view and a front view illustrating the pressure sensor.